Coal-fired space heater



e. w. HARDING COAL-FIRED SPACE HEATER Aug. 9

Filed Jan. 24, 1956 2 Sheets-s 1 INVE lWlli Q d y wi ATTOR Aug. 9, 1960e. w. HARDING COAL-FIRED SPACE HEATER 2 Sheets-Sheet 2 Filed Jan. 24,1956 INVENTOR ATTORNEYS United States Patent 2,948,276 COAL-FIRED SPACEHEATER- George W. Harding, Lynchburg, Va., assiguor to Automatic Draftand Stove Co., Inc., Lynchbu'rg, Va., a corporation of Virginia FiledJan. 24, 1956, Ser- No. 560,996

7 Claims. (Cl. 12"667) This invention relates to automaticallycontrolled coalfired space heaters, and more particularly to that typeof space heater in which the heat-actuated regulator is carried thereonfor regulating the draft entering below the grate bars by opening andclosing a damper positioned across the draft access.

Generally speaking, heaters of this type are provided for heatingnon-insulated, non-weatherstripped, drafty houses. It would be mostuneconomical, if not impossible, to adequately heat such houses with aspace heater responsive solely to room temperature. A more practicalmethod of operation is to provide a heating unit which responds to thetemperature of the stove rather than temperature of the room, and willcreate a zone of comfort in close proximity to the heater, so that theoccupants of the room may position themselves in the room according totheir requirements for comfort.

However, it has been found that where the thermostat on the draftregulator responds solely to the temperature of the stove there aretimes during low combustion within the combustion chamber when theresidual heat in the metallic parts of the stove lulls the thermostatinto remaining closed at a time when it should begin to open so as tostimulate the wanning fire before combustion becomes so feeble that thefire goesout. Since the room temperature is lower than the temperatureof the stove, even during low combustion periods, it follows that if thethermostat could be influenced to an extent by room temperature it wouldopen sooner than if stimulated solely by stove temperature, thusreviving a low' fire which might otherwise diminish to the point ofgoing out.

One of the objects of the present invention is to provide a coal-burningspace heater of the type in which draft for combustion is supplied frombeneath the grate regulated by a thermostatically controlled damperresponsive primarily to the temperature of the stove and secondarily byroom temperature, derived from the cooler strata of the room airentering the casing of the heater in a zone below the combustionchamber.

Another object of the invention is to provide a heater of the typedescribed, in which the temperature responsive draft unit is mounted onthe ash door of the heater, and includes a conduit communicating throughsaid door with the ash pit, the fuel door, which is above the draft unitbeing hinged at the bottom so as to overlie said conduit when said dooris open shielding said conduit from the entrance of spilled fuel. e

Other objects of the invention will become apparent from the followingdescription of a practical form when considered drawings.

In the drawings:

Figure 1 is a front perspective view of a warm air circulating type ofcoal fired space heater made in accordance with the present invention;

Figure 2 is a sectional view of a partial side elevation of the lowerfront portion of the space heater shown in in conjunction with theaccompanying "ice heater in accordance with the present invention isshown generally at 1, having a body 2. supported on a base 3 and havinga grate 4 transversely disposed therein at an intermediate leveldividing the said body into a combustion chamber 5 and an ashpit6. Thefuel door 7 which provides access to the combustion chamber is hinged atthe bottom permitting the door to swing downward when opened. The ashpitdoor 8 is hinged at one side permitting the door to swing open laterallyas shown in Figure 1. 7

The cabinet '9 completely surrounds the body and is spaced from it onall sides. The cold air louvres 10, 10' near the bottom of the cabinetgive access for the cold air from the room, which passes upward byconvection between the cabinet and the body. The upper inlet air louvres11-11' are provided to admit air from a warmer level of the room. toenter the heater. This air is quickly heated to a high temperature andinduces rapid circulation of air through the heater. The grill 12 at thetop of the heater is the outlet for the warm air. The front of thecabinet is formed with the door 13 to give access to the doors of thecombustion chamber and ashpit.

As shown in Figure 2, the ashpit door is provided with the draft accessopening 15 and the draft conduit 16 is secured to the outer facingthereof. The effective draft access is at the mouth 17 of the draftconduit 16, since the draft conduit'is extended upward a short distanceabove the opening 15 to a point just below the bottom of the fuel door7. This creates a slight upward convection pressure in the conduit 16which is easily overcome by the draft of the chimney, even under minimumcombustion conditions;

The damper 18 is fixed to the shaft 19 within the draft conduit 16 whichis pivotally journaled in the opposite walls of said conduit formovement through an arc of The peripheral frame 20 is secured within theconduit 16 having the flange 21 with its halves offset so that thedamper engages opposite faces of the flange when closed. p

The end 22 of the damper shaft 19'is extended beyond the draft conduit16. The thermostatic element 23 con sists of a bimetallic coil havingits inner end 24 attached to the end 22 of the damper shaft 19 and beingformed with a loop 25 at its opposite end constituting part of a pin andslot connection, as will appear.

The dial shaft 26 is journaled in the walls of the con- I duit 16beneath the damper shaft 19 in the same vertical plane and at suchdistance beneath it as to be in the path of movement of the damper,thereby acting as a stop for the damper when it is in full openposition." The dial 27 is mounted as shown, on one end of the dial shaft26 on the outside of the conduit 16 and the other end 28 of the dialshaft-26 has an upturned portion formed with a crank pin 29 which playswithin the loop 25 of the thermostatic element 23. The dial shaft 27 isspring loaded (not shown) to produce frictional resistance to rotationof the shaft sufficient to dominate the pull of the thermostaticelement, so that the crank pin becomes an anchor against which thethermostatic element thrusts in operating the damper; When the knob isturned, the position of the crank pin is changed, varying the point atwhich the 3 thermostatic element begins to be effective in controllingthe damper.

Incoming air passes into the cabinet through louvres 10, in the lowerzone of the cabinet, and before. it comes in contact with the walls ofthe body whichv surround the combustion chamber, the air in the lowerpart of the cabinet approximates the temperature of the lower strata ofair in the room, and the thermostatic element is located'in this zone ofcool air.

It will be noted that when fuel door 7 is in lowered position, itoverlies the mouth of the draft conduit 16 and shields it from theentrance of fuel particles spilled when stoking the combustion chamber.

In the present invention the relatively cold room air which enters thelouvres l0 and occupies the lower part of the cabinet chamber and whichis the source of draft of the conduit 16 passes over the thermostaticelement 23, so as to an extent to modify the influence of stovetemperature upon said thermostatic element. When the combustion isrelatively high, the ratio which the room temperature affecting thethermostatic element bears to the heater temperature is low, so that theetfect of the room temperature is negligible. However, when combustionin the heater is low, the ratio of the room temperature affecting thethermostat becomes relatively high, so that the room temperature becomesa material factor in inducing the thermostatic element to open thedamper sooner than would be the case if it remained subject only to:stove temperature. This provides increased draft and stimulatescombustion when the fire may be so low that otherwise it could not berevived.

In the modification shown in Figures 3 through 5, the access passage 31is formed in one side of the wall of the ashpit 6. The draft conduit 16is mounted at the passage 31, extends upwardly and terminates at a pointsubstantially at the level of the lower edge of the fuel door 7. Thedamper shaft 19 extends transversely of the conduit perpendicular to theouter wall thereof and extends beyond said outer wall. The thermostaticelement 23 is mounted on the extended end of the shaft 19.

The dial 2-7 is mounted on the outside of the cabinet 9 above thelocation of the thermostatic element. The dial shaft 32 is journaled inthe wall of the cabinet 9 and the dial 27 is mounted on the outer end ofthis shaft. The rotation of the dial 27 is frictionally retarded forthe'same purpose as described in connection with dial 27 in the firstdescribed modification. A rod 33 is fixedly attached to dial shaft 32 ata right angle thereto. A rod 34 is journaled in the cabinet and has anarm 34 bent at right angle thereto. The rod 34 is in axial alignmentwith the damper shaft 19, so that the arm 34' and loop 25 will traverseconcentric arcs. A link 35 has angularly disposed ends 36 and 37 bymeans of which it is pivotally connected, respectively, to the rods '33and 34. The end 3-6 is extended to pass through the loop 25 ofthermostatic element 23 and forms the pin which engages the loop 25 forrotating thermostatic element 23. This construction being the same asthat disclosed in the first described modification.

While in the above description there has been disclosed practicalembodiments of the invention, it will be understood that the inventionmay include other structural forms.

What is claimed is:

1. In a coal burning circulating space heater of the type having a bodywith a grate intermediately positioned therein defining therewith acombustion chamber above and an ash pi below the grate and having acabinet surrounding the body in spaced relation thereto with an airinlet opening in its lower part and a relatively high outlet openingtherethrough providing for circulation of room air between said body andsaid cabinet, the improvement comprising, a down draft conduit withinthe space between said body and cabinet positioned in heat receivingproximity to said combustion chamber to conduct primary air forcombustion downwardly into said ashpit and having its intake end openingwithin the space between said body and cabinet adjacent said combustionchamber and its outlet end communicating with said ash pit, a damperwithin said conduit and a bimetallic thermostat controlling said dampermounted on said conduit to be heated thereby, and so positioned as to bebathed by the relatively cool circulating air in transit from said airinlet opening to said air outlet opening.

2. In a coal burning circulating space heater of the type having a bodywith an intermediate grate therein defining therewith a combustionchamber above and an ash pit below the grate, and having a cabinetsurrounding the body in spaced relation thereto with an air inletopening through the lower part of said cabinet and a relatively highoutlet opening therethrough providing for circulation of air betweensaid cabinet and said body, the improvement comprising a laterallyswinging door giving access to said ash pit and a door hinged at thebottom, above said ash pit door, giving access to said combustionchamber, a down draft conduit extending upwardly from said ashpit andwithin the space between said body and said cabinet to conduct primaryair for combustion downwardly into said ashpit, said down draft conduitbeing mounted on said ash pit door, having its discharge endcommunicating with said ash pit through an aperture in said ash pitdoor, and being so extended as to be in heat exchanging relation to saidcombustion chamber, said conduit having its intake end opening withinsaid space between said body and said cabinet and terminating beneathsaid combustion chamber door, said combustion chamber door having arange of movement causing it when fully open to overlie the said inletend of said draft conduit whereby said combustion chamber door shieldssaid intake end of said draft conduit from spillage when fuel is beingplaced in said combustion chamber, a damper mounted in said conduit anda thermostat controlling said damper mounted in heat exchanging relationto said combustion chamber and positioned to be bathed by the relativelycool room air entering the space between said body and. cabinet.

3. A coal burning circulating heater comprising, a body having a grateintermediately positioned therein defining therewith a combustionchamber above and an ashpit below said grate, said ashpit having anaccess opening, said body having a fuel access opening above said ashpitopening, a laterally swinging door for said ashpit opening, a conduitfor downwardly directing draft carried by said ashpit door and openingtherethrough, having its inlet end terminating below the level of saidfuel access opening, a door for said fuel access opening hinged in ahorizontal axis at the bottom of said fuel access opening, said fuelaccess door being swingable to a position overlying said conduit andfunctioning as a shield for the inlet end thereof.

4. Coal burning circulating heater comprising, a body having a grateintermediately positioned therein defining a combustion chamber aboveand an ashpit below said grate, an air supply conduit exterior to saidbody communicating with said ashpit adjacent said grate and having anupright limb close to said body in the Zone of said combustion chamber,a damper shaft for said conduit journaled in the upper end of saidupright limb, a damper mounted on said damper shaft, a thermostatexterior to said conduit at the upper end of said upright limb andoperatively connected to the shaft of said damper, a fuel access doorfor said combustion chamber hinged at its bottom to said body on ahorizontal axis and positioned to open out in shielding relation to theupper end of said conduit.

5. Coal burning circulating heater comprising, a body having a grateintermediately positioned therein defining a combustion chamber aboveand an ashpit below said grate, an access door for said ashpit, an airsupply conduit exterior to said body carried by said ashpit door,

communicating with said ashpit adjacent said grate and having an uprightlimb normally close to said body in the Zone of said combustion chamber,a damper shaft for said conduit journaled in the upper end of saidupright limb, a damper mounted on said damper shaft, a thermostatexterior to said conduit at the upper end of said upright limb andoperatively connected to the shaft of said damper, a fuel access doorfor said combustion chamber above said ashpit door, hinged at its bottomto said body on a horizontal axis and positioned to open out inshielding relation to the upper end of said conduit.

6. In a coal burning circulating space heater of the type having a bodywith a grate intermediately positioned therein defining therewith acombustion chamber above and an ashpit below the grate and having acabinet surrounding the body in spaced relation thereto with an airinlet opening in its lower part and a relatively high outlet openingtherethrough providing for circulation of room air between said cabinetand said body, the improvement comprising, a draft conduit to conductprimary air for combustion downwardly into said ashpit and having anupwardly directed inlet and an outlet, said draft conduit inlet being insaid space between said body and said cabinet and adjacent saidcombustion chamber substantially medially of the horizontally projectedplane of said grate and the horizontally projected plane of the top ofsaid body, said draft conduit outlet being in communication with saidashpit, a damper for controlling the draft in said draft conduit, abimetallic thermostat for operating said damper mounted within the spacebetween said combustion chamber and cabinet in heat exchanging relationto said combustion chamber and in the path of convective flow of roomair through said space, and said thermostat being operatively connectedto said damper.

7. Coal burning circulating heater comprising, a base, an ashpitextending to a vertical height above said base, a combustion chamberextending to a vertical height above said ashpit, a grate transverselymounted at the intersection of said ashpit and said combustion chamber,a top surmounting said combustion chamber, a primary air supply conduithaving a lateral limb and an upright limb, said lateral limb being incommunication with said ashpit, said upright limb being spaced outwardlyfrom said ashpit and having a free end extending upwardly andterminating substantially below the medial height of said combustionchamber, a damped shaft journaled in the free end of said upright limbof said primary air supply conduit, a damper fixedly mounted on saiddamper shaft, a bimetallic thermostat mounted exteriorly of said conduitadjacent said free end of said upright limb, said thermostat beingoperatively coupled to said damper shaft, and a louvered cabinetsurrounding said ashpit and combustion chamber in spaced relationthereto and enclosing said primary air conduit and said thermostat insaid space.

References Cited in the file of this patent UNITED STATES PATENTS1,225,280 Skinner May 8, 1917 2,031,652 Hopping Feb. 25, 1936 2,227,689Agricola Ian. 7, 1941 2,394,441 Griswold Feb. 5, 1946 2,554,370 MartinMay 22, 1951 2,797,874 Harding July 2, 1957 FOREIGN PATENTS 725,059Great Britain Mar. 2, 1955

